A united front is an alliance of groups against their common enemies, figuratively evoking unification of previously separate geographic fronts and/or unification of previously separate armies into a front. The name often refers to a political and/or military struggle carried out by revolutionaries, especially in revolutionary socialism, communism, or anarchism. The basic theory of the united front tactic among socialists was first developed by the Communist International, an international communist organization created by communists in the wake of the October Revolution. According to the thesis of the 1922 4th World Congress of the Communist International:

The united front tactic is simply an initiative whereby the communists propose to join with all workers belonging to other parties and groups and all unaligned workers in a common struggle to defend the immediate, basic interests of the working class against the bourgeoisie.